Influence of prostaglandins, omeprazole, and indomethacin on healing of experimental gastric ulcers in the rat

Anti-ulcerogenic effect of chitin and chitosan on mucosal antioxidant defence system in HCl-ethanol-induced ulcer in rats

The anti-ulcerogenic effect of chitin and chitosan against ulcer induced by HCl-ethanol in male Wistar rats was studied. Levels of acid output, pepsin, protein, lipid peroxides and reduced glutathione and the activity of glutathione peroxidase (GPx), glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) were determined in the gastric mucosa of normal and experimental groups of rats. A significant increase in volume and acidity of the gastric juice was observed in the ulcer-induced group of rats. Peptic activity was significantly decreased as compared with that of normal controls. In the rats pre-treated with chitin and chitosan 2% along with feed, the volume and acid output and peptic activity of gastric mucosa were maintained at near normal levels. The level of lipid peroxidation was significantly higher in the ulcerated mucosa when compared with that of normal controls. This was paralleled by a decline in the level of reduced glutathione and in the activity of antioxidant enzymes like GPx, GST, CAT and SOD in the gastric mucosa of ulcer-induced rats. Also, the levels of mucosal proteins and glycoprotein components were significantly depleted in ulcerated mucosa. The pre-treatment with chitin and chitosan was found to exert a significant anti-ulcer effect by preventing all the HCl-ethanol-induced ulcerogenic effects in experimental rats.

Cytoprotection and healing: two unequal brethren

The promotion of the concept of cytoprotection has fostered hopes that the use of co-prescribed mucosal protective agents would revolutionize the prevention of NSAID-induced ulcers and supply the basis for novel ulcer therapy. Prostaglandins do not, however, accelerate ulcer healing when applied at doses that exert an unequivocal cytoprotective activity. Attempts have therefore been made in recent years to create new less-toxic NSAIDs, such as combined lipoxygenase/cyclo-oxygenase inhibitors, NSAIDs coupled to an NO donor and so-called COX-2 inhibitors. All these preparations do in fact exert a diminished gastrointestinal toxicity. There is however increasing evidence accumulating from studies performed in and outside our laboratories that in chromic ulcer models their increased gastrointestinal tolerance is not necessarily reflected by non-interference with ulcer healing. It is thus mandatory to distinguish between cytoprotective and healing properties of drugs interfering with the cyclo-oxygenase pathway.

Melatonin as pharmacologic support in burn patients: a proposed solution to thermal injury-related lymphocytopenia and oxidative damage

OBJECTIVE

To review the data that support the clinical use of melatonin in the treatment of burn patients, with special emphasis on the stimulation of the oxidative defense system, the immune system, circadian rhythm of sleep/wakefulness, and the reduction in the toxicity of therapeutic agents used in the treatment of burn victims.

DATA SOURCE

A MEDLINE/PubMed search from 1975 to July 2006 was conducted.

STUDY SELECTION

The screening of the literature was examined using the key words: burn patients, lymphocytopenia, skin oxidative stress, antioxidant, melatonin, and free radicals.

DATA EXTRACTION AND SYNTHESIS

Thermal injury often causes damage to multiple organs remote from the original burn wound and may lead to multiple organ failure. Animal models and burn patients exhibit elevated free radical generation that may be causative in the local wound response and in the development of burn shock and distant organ injury. The suppression of nonspecific resistance and the disturbance in the adaptive immune system makes burn patients vulnerable to infections. Moreover, there is loss of sleep and the toxicity produced by drugs habitually used in the clinic for burn patients. Melatonin is a powerful antioxidant and is a potent protective agent against damage after experimental thermal injury. Some actions of melatonin as a potential supportive pharmacologic agent in burn patients include its: role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes, reduction in proinflammatory cytokines, inhibition of adhesion molecules, chronobiotic effects, and reduction in the toxicity of the drugs used in protocols to treat thermal injury patients.

CONCLUSIONS

These combined actions of melatonin, along with its low toxicity and its ability to penetrate all morphophysiologic membranes, could make it a ubiquitously acting and highly beneficial molecule in burn patients.

The potential of melatonin in reducing morbidity-mortality after craniocerebral trauma

Craniocerebral trauma (CCT) is the most frequent cause of morbidity-mortality as a result of an accident. The probable origins and etiologies are multifactorial and include free radical formation and oxidative stress, the suppression of nonspecific resistance, lymphocytopenia (disorder in the adhesion and activation of cells), opportunistic infections, regional macro and microcirculatory alterations, disruptive sleep-wake cycles and toxicity caused by therapeutic agents. These pathogenic factors contribute to the unfavorable development of clinical symptoms as the disease progresses. Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine endogenously produced in the pineal gland and in other organs and it is protective agent against damage following CCT. Some of the actions of melatonin that support its pharmacological use after CCT include its role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes (e.g. superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase), inhibition of pro-inflammatory cytokines and activation-adhesion molecules which consequently reduces lymphocytopenia and infections by opportunistic organisms. The chronobiotic capacity of melatonin may also reset the natural circadian rhythm of sleep and wakefulness. Melatonin reduces the toxicity of the drugs used in the treatment of CCT and increases their efficacy. Finally, melatonin crosses the blood-brain barrier and reduces contusion volume and stabilizes cellular membranes preventing vasospasm and apoptosis of endothelial cells that occurs as a result of CCT.

Mechanisms involved in the gastro-protective effect of STW 5 (Iberogast) and its components against ulcers and rebound acidity

The protective effect of a commercial preparation (STW 5, Iberogast), containing the extracts of bitter candy tuft, lemon balm leaf, chamomile flower, caraway fruit, peppermint leaf, liquorice root, Angelica root, milk thistle fruit and greater celandine herb, against the development of gastric ulcers was previously reported in an earlier publication (Khayyal et al., 2001). All extracts produced a dose dependent anti-ulcerogenic effect associated with a reduced acid output, an increased mucin secretion, an increase in prostaglandin E(2) release and a decrease in leukotrienes. The effect on pepsin content was not uniform and did not seem to bear a relationship with the anti-ulcerogenic activity. The best effects were observed with the combined formulation, STW 5. Furthermore, the effect of the latter in protecting against the development of rebound gastric acidity was examined experimentally in rats and compared with the effect of some commercial antacid preparations (Rennie, Talcid and Maaloxan). A model of testing rebound acidity was developed by inducing a marginal increase in gastric acidity through the administration of indomethacin, in such a way that it could be easily neutralized, allowing any eventual secondary increase in acidity to be measured within a few hours of administration. In addition, the serum gastrin level was measured after drug treatment to establish any correlation between it and any rebound acidity. The results obtained demonstrated that STW 5 did not only lower the gastric acidity as effectively as the commercial antacid, but it was more effective in inhibiting the secondary hyperacidity. Moreover, STW 5 was capable of inhibiting the serum gastrin level in rats, an effect which ran parallel to its lowering effect on gastric acid production.

Regulated spatial distribution of cyclooxygenases and lipoxygenases in Crohn's ulcer

BACKGROUND AND AIMS

Arachidonic acid metabolism actively participates in the initiation, climaxing, and resolution phases of inflammation, and its close connection with inflammatory bowel diseases has been only recently discovered. We aimed to clarify the role of different arachidonic pathways and the interrelationships between them in Crohn's disease.

METHODS

Seventeen specimens of Crohn's disease dated between 2003/1/1 and 2005/1/1 were collected and underwent immunohistochemical analyses with cylcooxygenase 1, cyclooxygenase 2, 5-lipoxygenase, and 15-lipoxygenase-1 antibodies.

RESULTS

(1) The spatial distribution of the three leading enzymes in arachidonic acid pathway--cyclooxygenase 2, 5-lipoxygenase, and 15-lipoxygenase-1--followed sequential arrangement in Crohn's ulcer: neutrophils highly expressing 5-lipoxygenase were in the utmost surface which bordered the band of cyclooxygenase-2 expression that is located just beneath it, and in the lower layers and below the granulation region were eosinophils carrying 15-lipoxygeanse-1. (2) Cyclooxygenase-2 and 15-Lipoxygenase-1-positive cells formed two barrier-like structures that possibly inhibited neutrophil infiltration.

CONCLUSION

The regulated distribution indicated coordinated interplay between inflammatory cells and parenchymal cells, between arachidonic acid pathways, and between innate and adaptive immunity; and the barrier-like structures indicated protective roles for cyclooxygenase 2 and 15-Lipoxygenase-1 in Crohn's disease.

Physiopathologie des lésions gastro-duodénales induites par les anti-inflammatoires non stéroïdiens

The pathogenesis of the gastroduodenal lesions induced by non-steroidal anti-inflammatory drugs and aspirin is primarily caused by a reduction in mucosal blood flow, which is the consequence of inhibition of cyclooxygenase-producing vasodilator prostaglandins. The subsequent phase is adherence of leukocytes to the endothelium, which may depend on cyclooxygenase-2. Endothelial lesions accentuate the fall of mucosal blood flow and promote the inflammatory process in the gastric mucosa. The inflammatory process is amplified by expression of TNFalpha in polymorphonuclears induced by non-steroidal anti-inflammatory drugs. A few days after starting treatment, epithelial proliferation and increased mucosal blood flow, partly dependent on cyclooxygenase-2 and nitric oxide expression, compensates for the damaging process. Selective inhibitors of inducible cyclooxygenase-2 have reduced gastrointestinal toxicity, which could partially be explained by the protection effect of cyclooxygenase-2 on the gastrointestinal mucosa during inflammation or epithelial repair. Selective inhibitors may worsen inflammatory bowel disease. Non-steroidal inflammatory drugs and aspirin, but perhaps not selective inhibitors, increase the mucosal lesions associated with Helicobacter pylori-induced gastritis. Co-administration of selective inhibitors and aspirin leads to gastrointestinal toxicity equivalent to that of non-specific anti-inflammatory drugs.

Roles of inducible nitric oxide synthase in the development and healing of experimentally induced gastric ulcers

The roles of inducible nitric oxide synthase (iNOS) in the development and healing of gastric ulcers have not been fully characterized. We characterized iNOS expression in experimentally induced ulcers in rat and mouse stomachs and investigated the roles of iNOS using iNOS gene-deficient (iNOS-/-) mice and wildtype mice. Gastric ulcers were induced in rats and mice by the application of acetic acid and cryoinjury, respectively. iNOS expression was detected on days 1-7 and peaked 3 days after ulcer induction in the rat. iNOS-positive cells were distributed mainly among the infiltrating cells and fibroblasts in the ulcer bed. The almost similar courses of healing and iNOS expression were observed in the ulcers of mice. During the course of healing, the iNOS gene status did not affect cell proliferation in the healing zone or vessel formation in the ulcer bed. iNOS deficiency, however, caused larger ulcers and severer inflammation during ulcer healing; the clearance of inflammatory cells in the ulcer bed by apoptosis was also delayed when the ulcer was re-epithelialized in the iNOS-deficient mice. These results indicate that iNOS is expressed in the ulcer bed and that iNOS activity may play beneficial roles in the ulcer repair process, possibly by regulating inflammation.

Melatonin: reducing the toxicity and increasing the efficacy of drugs

Melatonin (N-acetyl-5-methoxytryptamine) is a molecule with a very wide phylogenetic distribution from plants to man. In vertebrates, melatonin was initially thought to be exclusively of pineal origin recent studies have shown, however, that melatonin synthesis may occur in a variety of cells and organs. The concentration of melatonin within body fluids and subcellular compartments varies widely, with blood levels of the indole being lower than those at many other sites. Thus, when defining what constitutes a physiological level of melatonin, it must be defined relative to a specific compartment. Melatonin has been shown to have a variety of functions, and research in the last decade has proven the indole to be both a direct free radical scavenger and indirect antioxidant. Because of these actions, and possibly others that remain to be defined, melatonin has been shown to reduce the toxicity and increase the efficacy of a large number of drugs whose side effects are well documented. Herein, we summarize the beneficial effects of melatonin when combined with the following drugs: doxorubicin, cisplatin, epirubicin, cytarabine, bleomycin, gentamicin, ciclosporin, indometacin, acetylsalicylic acid, ranitidine, omeprazole, isoniazid, iron and erythropoietin, phenobarbital, carbamazepine, haloperidol, caposide-50, morphine, cyclophosphamide and L-cysteine. While the majority of these studies were conducted using animals, a number of the investigations also used man. Considering the low toxicity of melatonin and its ability to reduce the side effects and increase the efficacy of these drugs, its use as a combination therapy with these agents seems important and worthy of pursuit.

Indomethacin delays gastric restitution: association with the inhibition of focal adhesion kinase and tensin phosphorylation and reduced actin stress fibers

Repair of superficial gastric mucosal injury is accomplished by the process of restitution-migration of epithelial cells to restore continuity of the mucosal surface. Actin filaments, focal adhesions, and focal adhesion kinase (FAK) play crucial roles in cell motility essential for restitution. We studied whether epidermal growth factor (EGF) and/or indomethacin (IND) affect cell migration, actin stress fiber formation, and/or phosphorylation of FAK and tensin in wounded gastric monolayers. Human gastric epithelial monolayers (MKN 28 cells) were wounded and treated with either vehicle or 0.5 mM IND for 16 hr followed by EGF. EGF treatment significantly stimulated cell migration and actin stress fiber formation, and increased FAK localization to focal adhesions, and phosphorylation of FAK and tensin, whereas IND inhibited all these at the baseline and EGF-stimulated conditions. IND-induced inhibition of FAK phosphorylation preceded changes in actin polymerization, indicating that actin depolymerization might be the consequence of decreased FAK activity. In in vivo experiments, rats received either vehicle or IND (5 mg/kg i.g.), and 3 min later, they received water or 5% hypertonic NaCl; gastric mucosa was obtained at 1, 4, and 8 hr after injury. Four and 8 hr after hypertonic injury, FAK phosphorylation was induced in gastric mucosa compared with controls. IND pretreatment significantly delayed epithelial restitution in vivo, and reduced FAK phosphorylation and recruitment to adhesion points, as well as actin stress fiber formation in migrating surface epithelial cells. Our study indicates that FAK, tensin, and actin stress fibers are likely mediators of EGF-stimulated cell migration in wounded human gastric monolayers and potential targets for IND-induced inhibition of restitution.

Effects of NSAIDs on cryoprobe-induced gastric ulcer healing in rats

BACKGROUND

Failure of ulcer healing may be critically important to the development of serious gastrointestinal complications in patients on long-term NSAIDs.

AIM

To determine the effect of indometacin, celecoxib, a cyclooxygenase-2-specific inhibitor, and nabumetone, a pro-drug, on ulcer healing rates in the rat.

METHODS

Gastric ulcers were induced using a cryoprobe. An NSAID or a vehicle control was administered to groups of eight rats for 3 or 6 days (2 mg/kg indometacin, 9 mg/kg celecoxib or 40 mg/kg nabumetone). The ulcer area was measured and epithelial proliferation at the ulcer margins was measured histochemically. The effect of the drugs on intestinal prostaglandin levels was also assessed.

RESULTS

The mean ulcer sizes in the four groups on day 3 were comparable. On day 6, control animals and those receiving nabumetone showed significant ulcer healing (P < 0.02), while the mean ulcer sizes in the indometacin (P < 0.01) and celecoxib (P < 0.02) groups were significantly larger than those in the control group. Higher doses of nabumetone (160 mg/kg), however, impaired healing. Intestinal prostaglandins were reduced (P < 0.01) only in indometacin-treated animals. The epithelial proliferation index was significantly lower among indometacin- (P=0.02) and celecoxib-treated (P=0.03) animals compared to controls at day 3.

CONCLUSIONS

Celecoxib and indometacin both decreased the epithelial proliferative response and delayed healing of cryoprobe-induced gastric ulcers. In contrast, nabumetone impaired ulcer healing only at very high doses.

[Changes in ulcerogenic response to non-steroidal anti-inflammatory drugs (NSAIDs) in adjuvant arthritic rats]

Gastroenteropathy is the most common among patients who use non-steroidal anti-inflammatory drugs (NSAIDs) for the treatment of inflammatory disorders. It is known that rheumatoid arthritic (RA) patients are more susceptible to NSAID-induced gastropathy than other NSAID users. This article reviewed our recent studies concerning the influence of arthritis on gastric mucosal integrity in adjuvant-induced arthritic rats. The gastric mucosal lesions induced by indomethacin, one of conventional NSAIDs, were markedly aggravated in arthritic rats. Likewise, the healing of chronic gastric ulcers induced by thermal cauterization was significantly delayed in arthritic rats. The underlying mechanisms of these phenomena observed in arthritic rats may be attributable to the enhancement of iNOS/NO pathway in the former and the less expression of various growth factors in the ulcerated mucosa, such as basic fibroblast growth factors (bFGF) or insulin-like growth factors (IGF-1) in the latter. In addition, we recently found that cyclooxygenase-2 (COX-2) selective inhibitors, such as rofecoxib or celecoxib, induced apparent gastric lesions in arthritic rats, suggesting that a caution should be paid on the use of COX-2 selective inhibitors in RA patients.

Indomethacin inhibits endothelial cell proliferation by suppressing cell cycle proteins and PRB phosphorylation: a key to its antiangiogenic action?

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit angiogenesis in vivo and in vitro, but the mechanism of this action is unclear. Angiogenesis-formation of new capillary vessels-requires endothelial proliferation, migration, and tube formation. It is stimulated by basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). The cell cycle is regulated positively by cyclins and negatively by cyclin-dependent kinase inhibitors (CKI) and the retinoblastoma protein (pRb). Since the effects of NSAIDs on cell cycle-regulatory proteins in endothelial cells remain unknown, we examined the effect of indomethacin on bFGF-stimulated endothelial cell proliferation and on cell cycle regulatory proteins in rat primary aortic endothelial cells (RAEC). Indomethacin significantly inhibited basal and bFGF-stimulated endothelial cell proliferation. This inhibition correlated significantly with reduced cyclin D1 and increased p21 protein expression. Furthermore, indomethacin reduced pRb phosphorylation. These findings suggest that indomethacin arrests endothelial cell proliferation essential for angiogenesis by modulating cell cycle protein levels.

The effects of omeprazole on healing and appearance of small gastric and duodenal lesions during dosing with diclofenac in healthy subjects

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are associated with gastrointestinal mucosal damage. Omeprazole prevents the formation, and accelerates the healing, of NSAID-induced ulcers.

AIM

To test whether omeprazole accelerates healing of standardized gastroduodenal lesions in the presence of diclofenac.

METHODS

In a double-blind, double-dummy, placebo-controlled, crossover study, 12 healthy volunteers received consecutive, 2-week courses of omeprazole (40 mg o.d.) and placebo, in random order, with an intervening, 4-week washout period; diclofenac (50 mg t.d.s.), was given for the second week of each course. Five endoscopies were performed, one at the outset and the others before and after each course of diclofenac. Biopsies were taken from the endoscopically normal mucosa of the corpus, antrum and duodenum and also from any new mucosal lesion that developed after diclofenac. The sites of biopsies taken before each course of diclofenac were evaluated endoscopically after each course to assess the extent of healing according to a predetermined healing score scale.

RESULTS

The healing scores observed after administration of placebo/diclofenac (median=0; range 0-6) and after omeprazole/diclofenac (median=0; range 0-6; P=0.17) did not differ. Small gastroduodenal lesions developed de novo in six subjects during placebo/diclofenac and in seven during omeprazole/diclofenac. Focal chemical gastropathy was observed only in close proximity to macroscopic lesions.

CONCLUSIONS

In healthy subjects, omeprazole does not accelerate the healing of pre-existing mucosal lesions or prevent the development of small diclofenac-induced mucosal lesions.

HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway

Although it is established that growth factors and prostaglandins function in the maintenance of gastric mucosal integrity and in the healing of gastric mucosal injury and ulceration, the regulatory relationship between growth factors and prostaglandins in the gastric mucosa is not well characterized. Therefore, we investigated whether hepatocyte growth factor (HGF) affects expression of COX-2 (the inducible form of the prostaglandin synthesizing enzyme, cyclooxygenase) in gastric epithelial cells and whether this action is mediated through the MAP (ERK) kinase signaling pathway. In RGM1 cells (an epithelial cell line derived from normal rat gastric mucosa), HGF caused an increase in COX-2 mRNA and protein by 236% and 175%, respectively (both P<0.05). This induction of COX-2 expression was abolished by pretreatment with the MAPK kinase (MEK) inhibitor PD98059. HGF also triggered a 13-fold increase in c-Met/HGF receptor phosphorylation (P<0.005) and increased ERK2 activity by 684% (P<0.01). Pretreatment with PD98059 abolished the HGF-induced increase in ERK2 activity, but not c-Met/HGF receptor phosphorylation. The specific inhibitor of p38 MAP kinase, SB203580, had no effect on HGF-induced COX-2 expression. Thus, HGF triggers activation of the COX-2 gene in gastric epithelial cells through phosphorylation of c-Met/HGF receptor and activation of the ERK2 signaling pathway.-Jones, M. K., Sasaki, E., Halter, F., Pai, R., Nakamura, T., Arakawa, T., Kuroki, T., Tarnawski, A. S. HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway.

Effects of S-0509, a novel CCKB/gastrin receptor antagonist, on acid secretion and experimental duodenal ulcers in rats

BACKGROUND

S-0509, 2-[(tert-butoxycarbonylmethyl) [(m-(carboxy-phenyl)-ureidomethyl-carbonyl]] aminobenzo phenone, was developed as a potent and selective CCKB/gastrin receptor antagonist that does not affect the central nervous system.

METHODS

We evaluated the effects of S-0509 on gastric acid secretion and duodenal ulcerogenic and healing responses in rats comparing it with L-365,260, another CCKB/gastrin receptor antagonist.

RESULTS

S-0509 (0.1 approximately 10 mg/kg, i.d.) was able to dose-dependently decrease basal acid secretion and inhibit the acid secretory responses induced by both pentagastrin (60 microg/kg/h, i.v.) and peptone (10%, i.g.) but not histamine (4 mg/kg/hr, i.v.) or carbachol (60 microg/kg/h, i.v.). L-365,260 (10 and 30 mg/kg, i.d.) caused only partial a suppression of the acid secretory response to pentagastrin but not to other stimuli, including peptone treatment. On the other hand, a duodenal ulcerogen, mepirizole (200 mg/kg, s.c. ) caused an increase in acid secretion and resulted in penetrating ulcers in the proximal duodenum, and these ulcers gradually healed over 3 weeks. S-0509 significantly inhibited both the acid secretory (> 1.0 mg/kg, i.d.) and ulcerogenic (> 3 mg/kg, p.o.) responses induced by mepirizole when it was given as a pre-treatment. It also promoted significantly the healing of these ulcers (> 3 x 2 mg/kg, p. o.) when it was given twice daily for 14 days. In contrast, L-365, 260 (30 mg/kg) tended to reduce the severity of mepirizole-induced duodenal ulcers, with a slight inhibition of acid secretion, but it caused no influence on the healing response of these ulcers.

CONCLUSION

These results confirmed that S-0509 is a selective CCKB/gastrin receptor antagonist with potent antisecretory action in vivo conditions, and further demonstrated that this agent not only prevents the development of duodenal ulcers but also shows healing promoting action on duodenal ulcers, probably through the blockade of CCKB/gastrin receptors.

Recombinant human transforming growth factor beta 3 accelerates gastric ulcer healing in rats

BACKGROUND

Gastric ulcer healing is mediated by various endogenous growth factors. In this experimental study effect of locally and systemically applied recombinant human transforming growth factor beta 3 (rhTGF-beta 3) on gastric ulcer healing was investigated in the rat.

METHODS AND RESULTS

Gastric ulcers were induced with a cryoprobe, and ulcer healing was evaluated 7 days after local infiltration (0.5 micrograms, 1.0 microgram, 2.5 micrograms, and 50 micrograms) or systemic (intravenous) application of TGF-beta 3 (500 micrograms/kg body weight). Compared with controls, a dose-dependent stimulation of ulcer healing (as evidenced by a reduction in ulcer size) was observed 7 days after local infiltration of TGF-beta 3 (1.0 microgram, 2.5 micrograms, and 50 micrograms). Corresponding increases in the levels of proliferating cell nuclear antigen (PCNA) and intracellular TGF-beta 3 expression and a downregulation of the TGF-beta type-II receptor expression were also observed in the granulation tissue of the ulcer margins. Systemic application of TGF-beta 3 produced effects similar to those observed after local treatment with 50 micrograms of the compound.

CONCLUSION

Local and systemic TGF-beta 3 treatment accelerates gastric ulcer healing in rats.

Reversion by histamine H2-receptor antagonists of plasma membrane alterations in ethanol-induced gastritis

Ethanol administration rapidly damages surface epithelial cells of rat stomach, leading to altered cellular plasma membranes. Histamine H2-receptor antagonists (H2RA) have been shown to have preventive properties against ethanol-induced gastric mucosal injury. Therefore, the possible reverting properties of H2RA (cimetidine, ranitidine, and famotidine) were tested in ethanol-induced gastritis. Subchronic ethanol administration elicited a histological profile of gastritis and alterations at the plasma membrane level (diminution of some phospholipids, increased cholesterol, and decreased activity of 5'-nucleotidase). H2RA administration to rats with gastritis promptly corrected the ethanol-induced mucosal damage. In addition, cytosolic enzyme activities (alcohol and lactate dehydrogenases) were also modified by gastritis and treatment with H2RA. In conclusion, our data suggest that H2RA improved restitution of the gastric mucosa contributing to the healing process of the gastric damage. The latter indicates reverting properties of H2RA on gastric damage, as well as their cytoprotective effect already described.

Indomethacin treatment during initial period of acetic acid-induced rat gastric ulcer healing promotes persistent polymorphonuclear cell-infiltration and increases future ulcer recurrence. Possible mediation of prostaglandins

The study was performed to examine whether indomethacin administered during the initial period of acetic acid-induced gastric ulcer healing affects future ulcer recurrence. Gastric ulcers were produced in rats by subserosal injection of acetic acid. Indomethacin (1 mg/kg/day, orally) administered either alone or concomitant with ornoprostil (50 micrograms/kg/day, orally) was started on the fourth day and continued for 56 days. In rats whose ulcer healed at the 90th day after production of ulcer, endoscopy was done every 30 days to examine recurrence of ulcer. Gastric specimens were obtained 10, 30, 60, 90, and 240 days after ulcer production for histology, to quantitate the height of regenerated mucosa, thickness of fibrous tissue, degree of polymorphonuclear cell infiltration, and PAS-positive cells. Cumulative ulcer recurrence rate was significantly higher in rats initially treated with indomethacin than in controls. Increased polymorphonuclear cell infiltration was the major histologic abnormality persisting after cessation of indomethacin. Ornoprostil reversed these abnormalities caused by indomethacin. In conclusion, the administration of indomethacin during the initial period of the ulcer healing promoted persistent polymorphonuclear cell infiltration and increased ulcer recurrence rates, possibly via a prostaglandin-dependent mechanism.

Effects of leminoprazole, omeprazole and sucralfate on indomethacin-induced delayed healing of kissing gastric ulcers in rats

We have examined whether or not repeated treatment with indomethacin delays the healing of kissing gastric ulcers induced in rats. The effects of leminoprazole, omeprazole and sucralfate on any delay in ulcer healing caused by indomethacin were also determined in relation to myeloperoxidase activity. Kissing gastric ulcers were induced by luminal application of an acetic acid solution. Indomethacin significantly delayed ulcer healing in a dose-dependent manner. Leminoprazole and omeprazole decreased the size and depth of ulcers, the healing of which was delayed by indomethacin, while sucralfate only decreased the ulcer depth. Histological studies showed that indomethacin inhibited tissue contraction and regeneration of the ulcerated mucosa. Leminoprazole and omeprazole prevented the inhibition of these parameters. The myeloperoxidase (MPO) activity of the ulcer portion in animals treated with indomethacin was markedly higher than in the control group. Both leminoprazole and omeprazole, but not sucralfate, significantly reduced MPO activity in contrast to the control value (in the presence of indomethacin). There was a significant relationship between the ulcerated area and myeloperoxidase activity. These results suggested that: (i) leminoprazole and omeprazole prevent the indomethacin-induced delay in ulcer healing by promoting tissue contraction and regeneration of the ulcerated mucosa; (ii) sucralfate prevents the indomethacin-induced delay in ulcer healing via the promotion of the formation of granulation tissue; and (iii) MPO activity will be useful to biochemically ensure the healing state of ulcers.

NSAID-induced delay in gastric ulcer healing is not associated with decreased epithelial cell proliferation in rats

Nonsteriodal antiinflammatory drugs initiate gastric ulceration and delay gastric ulcer healing. This study aimed to investigate the role of epithelial cell proliferation in delayed ulcer healing and to identify the most reproducible technique for measuring cell proliferation. Rats with acetic acid-induced gastric ulcers were treated for two weeks with indomethacin (1 mg/kg), aspirin (200 mg/kg), or vehicle control. Ulcers were assessed by macroscopic measurement of ulcer area, quantitative histological measurement of mucosal regeneration, and 5-bromo-2'-deoxyuridine immunohistochemistry to assess epithelial cell proliferation. Indomethacin and aspirin significantly delayed ulcer healing and inhibited mucosal regeneration. Three techniques for assessing cell proliferation were compared, and a scoring system, designed to take into account the entire tissue, was shown to be the most reproducible technique. Indomethacin significantly enhanced cell proliferation in the fundic area of ulcer and aspirin had no effect on cell proliferation. We conclude that aspirin and indomethacin delay ulcer healing by an inhibition of mucosal regeneration, but they do not inhibit epithelial cell proliferation.

Indomethacin inhibits cell proliferation and increases cell losses in rat gastrointestinal epithelium

Gastrointestinal cell proliferation was estimated in histological sections of rats treated with low and high doses of parenteral indomethacin for 3 to 60 days. Mitoses were arrested with vincristine and cells in S phase were labeled with tritiated thymidine. Short-term, low-dose treatments reduced the mitotic activity in the oxyntic and small intestinal epithelium, whereas moderate doses restored the mitotic index and high doses increased the proliferative activity and produced epithelial hyperplasia. Long-term, low-dose treatments increased cell proliferation in the small intestine and reduced the number of villous cells. Indomethacin did not affect the proliferative response elicited by refeeding in the oxyntic mucosa, but the simultaneous administration of prostaglandin E2 analog increased the number of arrested mitoses. The turnover of labeled cells was accelerated by indomethacin, particularly in the small intestine. These findings indicate that prostaglandins are regulators of the cell kinetics of the gastrointestinal epithelium but, at the same time, they disclose the presence of trophic mechanisms that are independent of the synthesis of endogenous prostaglandins.

Changes in gastric function and healing of chronic gastric ulcers in aged rats

The present study was designed to determine the relationship between changes in gastric function caused by aging and the healing of gastric ulcers. Male Fischer-344 rats (young, 2 months; aged, 24-26 months) were used. Gastric ulcers were induced by luminal application of an acetic acid solution (60%, 0.2 ml, 45 sec). The basal and histamine-stimulated gastric acid secretions in aged animals were significantly lower than those in young animals. However, the serum gastrin levels were almost the same in the two groups. Gastric mucosal blood flow and mucosal cell proliferation were also decreased in aged animals. Gastric contractile activity induced by electrical vagal stimulation was almost the same in the two groups, while the gastric relaxative response was significantly reduced in aged animals. The development and healing rate of gastric ulcers in aged animals were almost the same as those in young animals. Histologically, regeneration of the ulcerated mucosa was significantly reduced and tissue contraction occurred in aged animals, as compared to in young animals. We concluded that aging had little or no influence on the development and healing rate of gastric ulcers in rats, but the quality of ulcer healing was quite different between young and aged animals, probably resulting from various gastric dysfunctions related to ulcer healing.

Mechanisms of mucosal injury and healing: the role of non-steroidal anti-inflammatory drugs

Biological insights into injurious effects of non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin (ASA), on mucosal protection and repair, are largely from studies of acute injury. That chronic ulceration is similar is not established. NSAIDs directly injure tissues, including endothelia, and at the same time impair the operation of many of the processes that normally contribute to mucosal protection, whatever the injurious agent. Many protective processes are mediated through prostaglandins, whose synthesis is abolished by inhibition of the constitutive isoenzyme, cyclooxygenase I (COX I) or Prostaglandin H-Synthase1 (PGHS1). The aims of therapy are aimed at inhibiting the inducible isozyme cyclooxygenase II (COX II) or prostaglandin-H Synthase2 (PGHS2), which contributes to prostanoid synthesis at sites of inflammation. Newer NSAIDs, selectively inhibiting COX II, promise to revolutionize the treatment of inflammatory disease while reducing mucosal injury. Meanwhile, there is increasing evidence that direct injury to both mucosae and endothelia is mediated by free-radical species, exacerbated by reduced blood flow, and by the local release of inflammatory and other mediators, which accentuate vascular leakage and hemorrhage, and cause intravascular aggregation of blood elements, stasis, hypoxia, and additional free-radical injury. The NSAIDs also inhibit epithelial cell division and the angiogenesis critical to healing and repair.

Persistent lack of somatostatin receptors in gastric mucosa of healing ulcers in rats

BACKGROUND/AIMS

Growth factors and their receptors play a role in healing ulcers of the rat. Somatostatin is a putative growth factor in the gastric mucosa with multiple functions mediated by specific receptors. Therefore, the distribution of somatostatin receptors was evaluated in the gastric mucosa of healing ulcers.

METHODS

Somatostatin receptors were measured in the gastric mucosa of healthy rats and of rats with cryoulcers and acetic acid-induced ulcers, using somatostatin receptor autoradiography with 125I-[Tyr3]-octreotide or 125I-[Leu8, D-Trp22, Tyr25]-somatostatin-28 as radioligands. Epidermal growth factor receptors were measured on adjacent sections with 125I-epidermal growth factor.

RESULTS

High-affinity somatostatin receptors are present in the gastric fundic mucosa of healthy rats. In contrast, in healing ulcers, the somatostatin receptors are almost lacking in the ulcer edge or scar at 3, 7, 28, 49, and even 84 days after ulcer induction (83%-91% reduction). Similar results are obtained with cryoulcers and with acetic acid-induced ulcers. For comparison, the number of epidermal growth factor receptors are increased in the same healing ulcers.

CONCLUSIONS

The persistent absence of somatostatin receptors for several months after ulcer induction may be of pathophysiological significance in ulcer repair and healing.

Biochemical evaluation of the antiulcerogenic effect of Cauvery-100 (an ayurvedic formulation) in rats

Due to the varied pathogenesis of ulcers, a number of pharmacologically different antiulcer drugs are now used in the treatment of the condition. The suitability of certain of these drugs is still to be established. Cauvery-100 is an ayurvedic formulation consisting of plant ingredients, and has been suggested to be useful in the treatment of gastrointestinal disorders. In the present study this drug was tested for its antiulcerogenic effect. The number of lesions on gastric mucosa decreased markedly after 15 days oral treatment with Cauvery-100 in rats with indomethacin-induced ulcers. The volume and total acidity of the gastric juice also decreased in the treated rats. The hexose, hexosamine and sialic acid levels of gastric contents, which were increased in untreated rats returned to near normal levels after 15 days of treatment. Protein in the gastric juice was elevated in untreated rats but returned to near normal levels after 15 days of treatment. Cauvery-100 acts both to decrease the acidity and to increase the mucosal defence in the gastric areas, thereby justifying its use as an antiulcerogenic agent.

Transendoscopic electrocautery-induced gastric ulcers as a model for gastric healing studies in ponies

The ponies were apparently healthy and 6-20 months of age. In Study 1, gastric lesions were created by transendoscopic electrocautery in the non-glandular gastric mucosa, adjacent to the margo plicatus in 9 ponies which were then treated with water, 12 mg cimetidine HCl/kg bwt or 18 mg cimetidine HCl/kg bwt per os every 12 h for 35 days. In Study 2, gastric lesions were similarly induced in 9 ponies in the non-glandular mucosa and also in the glandular mucosa just below the non-glandular lesion on the greater curvature of the stomach. The ponies were treated with water, 8 mg cimetidine/kg bwt or 16 mg cimetidine/kg bwt per os every 8 h for 21 days. In both studies gastric lesion healing was monitored twice weekly by video gastroscopy. There was no apparent difference in healing times between the water and cimetidine treatment groups in either study. These results indicate that uniform gastric ulcers can be created by transendoscopic electrocautery in the non-glandular mucosa of ponies and that these ulcers heal at a predictable rate which should be useful in studying compounds that might accelerate healing of gastric mucosal lesions. However, cimetidine was not effective in accelerating the rate of healing under the conditions of this study.

Review article: controversies in NSAID-induced gastroduodenal damage--do they matter?

BACKGROUND

This article reviews various issues surrounding NSAID-induced gastroduodenal ulceration, about which there appear to be conflicting views and data in the literature. These issues include the size, clinical relevance and main site of the problem; when complications occur (early or late?); the relevance of non-ulcer lesions and whether adaptation is a clinically relevant phenomenon.

METHOD

A comprehensive literature search was carried out to identify relevant new data published since 1987.

RESULTS

NSAIDs are causally associated with more gastric than duodenal ulcers but their use may be associated with duodenal ulcers or complications. Erosive lesions may progress to more severe damage. The theories of early or late onset of complications during a course of NSAID therapy may not be mutually exclusive.

CONCLUSIONS

Available data indicate that NSAID ulcers are at least as dangerous as classic peptic ulcers, and result in significant morbidity and mortality which in the patient population does not appear to be significantly reduced by processes such as adaptation.

Effects of nonsteroidal anti-inflammatory drugs and misoprostol on gastroduodenal epithelial proliferation in arthritis

In this study, quantitation of the epithelial proliferation status of gastric glands and duodenal crypts was performed using endoscopic biopsy specimens from patients with rheumatological conditions requiring long-term anti-inflammatory and analgesic therapy, testing the hypothesis that long-term administration of nonsteroidal anti-inflammatory drugs (NSAIDs) may lead to enhanced epithelial cell proliferation in the stomach and duodenum. After a 1-week washout period from NSAID administration, specimens were taken from endoscopically normal gastric antrum and duodenum, and microdissection was used to quantitate mitoses in these sites. Endoscopy and biopsy were then repeated after 2 weeks of NSAID administration, during which patients received in addition either the prostaglandin E1 analogue misoprostol (10 patients) or a placebo (10 patients). Mitotic counts in gastric glands increased similarly and significantly in the two groups from (mean +/- SEM) 4.45 +/- 0.57 to 7.69 +/- 1.08 (P less than 0.001) in the NSAID+placebo-treated group and from 4.31 +/- 0.53 to 7.68 +/- 1.08 (P = 0.006) in the NSAID+misoprostol-treated group. Similar changes took place in the duodenal crypts, from 5.44 +/- 0.68 to 8.60 +/- 1.28 (P = 0.013) in the NSAID+placebo-treated group and from 4.68 +/- 0.56 to 6.35 +/- 0.63 (P = 0.011) in the NSAIDs+misoprostol-treated group. NSAIDs increased the proportion of glands and crypts with bifid or more complex architectural forms. In a small group of patients, misoprostol alone did not alter mitotic rate in glands or crypts over 4 weeks. Thus, NSAIDs increase the rate of proliferation in endoscopically normal gastric and duodenal epithelium of patients with arthritis. This may form one of the mechanisms underlying gastric and duodenal adaptation to NSAIDs.

Quality of gastric ulcer healing: histological and ultrastructural assessment

It has long been assumed that the mucosa in areas of grossly 'healed' gastric or duodenal ulcers returns to normal, either spontaneously or after treatment. This assumption is based almost entirely upon visual, superficial examination by endoscopy. Few, if any, histological and ultrastructural studies examined the deeper mucosa in the areas of grossly healed ulcers. In several experimental studies, we analysed the development, evolution, and healing of acetic acid-induced gastric ulcers in rats and assessed the histological and ultrastructural features (structure and cellular composition) of the gastric mucosa in areas of grossly healed ulcers. The gastric mucosa of grossly 'healed' ulcers showed re-epithelialization of the mucosal surface at every study interval (2 weeks, 2, 3, and 4 months), but the subepithelial mucosa displayed prominent abnormalities. Two patterns of scarring were distinguished: (a) the mucosa in the area of healed ulcer was thinner (25-45% thinner than normal mucosa) with increased connective tissue and poor differentiation and/or degenerative changes in the glandular cells; and (b) the mucosa displayed a marked dilation of gastric glands with poor differentiation of the glandular cells and a reduction in the supportive microvascular network. It is theorized that these abnormalities could interfere with oxygenation, nutrient supply, and mucosal resistance and defence; therefore, they could be a basis for ulcer recurrence. These observations indicate that the quality of mucosal structural restoration rather than the speed of ulcer healing is the most important factor in determining risk of ulcer recurrence. The clinical relevance of these findings is supported by a preliminary study in which marked histological abnormalities were found in the subepithelial mucosa in patients with 'healed' duodenal ulcers.

Relationship between gastric mucosal prostaglandin levels and healing of gastric lesions in rats

1. This study was designed to determine whether or not endogenous prostaglandins (PG) contribute to the healing of gastric ulcers induced by high concentrations of ethanol or water immersion stress. 2. Ethanol-induced gastric lesions; rats were divided into four groups: (1) the control group: untreated; (2) the indomethacin group: indomethacin (2 mg/kg) was injected intramuscularly (i.m.) once daily until the end of the experiment; (3) the ethanol group: rats were given 1 mL of 50% ethanol intragastrically; (4) the ethanol + indomethacin group: indomethacin (2 mg/kg) was injected (i.m.) once daily from 1 h after administration of 50% ethanol until the end of the experiment. 3. Water immersion stress-induced gastric lesions; rats were divided into three groups: (1) control group: untreated; (2) stress group: rats were placed in a stress cage and immersed into a water bath (23 degrees C) for 6 h; (3) stress + indomethacin group: indomethacin (2 mg/kg) was injected (i.m.) once daily for 3 consecutive days immediately after stress treatment or from 3 days after stress treatment until the end of the experiment. 4. Immediately after observation of the lesions, the fundic mucosal layer was separated from the muscle layer and mucosal PG levels were measured by high performance liquid chromatography in each group. 5. Indomethacin did not inhibit ulcer healing until 48 h after administration in the ethanol experiment, and until 3 days after administration in the water immersion experiment. In contrast, indomethacin inhibited ulcer healing thereafter in each experiment respectively. 6. Four kinds of PG, that is 6-keto-PGF1 alpha, PGF2 alpha, PGE2 and PGD2 were detected in gastric mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of non-steroidal anti-inflammatory drugs on mucosal cell proliferation associated with gastric ulcer healing

To find out whether non-steroidial anti-inflammatory drugs (NSAIDs) inhibit the proliferation of mucosal cells that normally leads to healing of gastric ulcers a microdissection technique was used to quantify mitosis in gastric glands at the ulcer edge in relation to that in the adjacent mucosa. The regeneration index thus obtained of the ulcer edge was greater in the 9 subjects with gastric ulcers not taking NSAIDs (mean index 3.1 [SEM 0.61]) than that in the 8 patients taking NSAIDs (index 1.49 [0.16]). In rats in which gastric ulcers were produced with a cryoprobe, the ulcers were larger and slower to heal in those receiving indomethacin than in controls; also, immunohistochemical staining indicated significantly fewer mitotic cells in glands adjacent to the ulcer in indomethacin-treated rats (8 mitoses [SEM 3]) than in control animals (25 [5]). The prostaglandin E1 analogue misoprostol reversed the inhibition of healing and substantially restored the proliferative rate in the animals. Inhibition of epithelial cell division normally involved in gastric ulcer healing would contribute to the high prevalence of gastric ulcer during NSAID therapy.

Effects of zinc L-carnosine on gastric mucosal and cell damage caused by ethanol in rats. Correlation with endogenous prostaglandin E2

The effects of zinc L-carnosine on ethanol-induced damage and the correlation of these effects with endogenous prostaglandin E2 were evaluated in rat gastric mucosa in vivo and in vitro. When given either intragastrically or intraperitoneally, zinc L-carnosine (10 or 30 mg/kg) prevented gross visible damage to gastric mucosa caused by ethanol without affecting the mucosal prostaglandin E2 level. This protective effect of zinc L-carnosine was not inhibited by indomethacin. Histological assessment showed that zinc L-carnosine inhibited deep mucosal necrosis, as did 16,16-dimethyl prostaglandin E2. Zinc L-carnosine (10(-6) or 10(-5) M) inhibited the damage caused by ethanol to gastric cells isolated from rat gastric mucosa in vitro; this effect was not inhibited by indomethacin. The results suggested that zinc L-carnosine protects the gastric mucosa and enhances cellular resistance to ethanol without the mediation of endogenous prostaglandins.

Mechanisms of gastroprotection

Gastric mucosa is constantly exposed to various irritants, but it usually maintains its integrity owing to several lines of defense, including mucus-alkaline secretion, mucosal hydrophobicity, rich mucosal blood flow, stabilization of tissue lysosomes, maintenance of mucosal sulfhydryls, and rapid proliferation and renewal of mucosal cells. Prostaglandins (PG) inhibit experimental gastric mucosal damage and ulcerations induced by a wide variety of agents, hence PG have been proposed to contribute to the overall protective process by activation of various mucosal defence lines--particularly by prevention of vasocongestion, ischemia, and deep hemorrhagic necrosis. The relation between tissue PG generation and mucosal protection does not appear to be closely related, and probably only minute amounts of PG are required to maintain mucosal integrity. In contrast to PG, other products of arachidonate metabolism, such as TxA2, LTC4 or LTD4, and the related lipid, platelet-activating factor, appear to mediate mucosal damage mainly by the disturbance in mucosal microcirculation and tissue ischemia. Gastroprotection can be achieved by stimulation of mucosal biosynthesis of protective PG or by the inhibition of the release or action of the proulcerogenic arachidonate metabolites. Certain natural substances, such as sulfhydryls, epidermal growth factor, or polyamines, protect the mucosa via a PG-independent mechanism, probably by enhancing the tissue repair processes.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of mucosal prostaglandin levels in healing of water immersion-induced gastric ulcers in rats

This study was designed to clarify the recovery time course of water immersion stress ulcers. Rats were divided into two groups: the control group and the cetraxate group. In the cetraxate group, 6 h after water immersion stress, cetraxate (300 mg/kg) was administered intragastrically twice a day until the end of the experiment. Ulcer indices were observed immediately, 1, 3, 7, 14, and 21 days after water immersion stress in each group. Changes in gastric mucosal prostaglandin (PG) levels were measured by means of high-performance liquid chromatography. In the control group ulcer healing was not observed within 1 day after stress. Gastric lesions had decreased significantly after 3 days, but 21 days were required for total healing. Accelerated ulcer healing was observed in the cetraxate group. Four kinds of PGs were detected in gastric mucosa: 6-keto-PGF1 alpha, PGF2 alpha, PGE2, and PGD2. Recovery of PG levels differed from each other. Fourteen days were required for full recovery of PGD2 and 6-keto-PGF1 alpha. In contrast, 7 days were required for recovery of PGF2 alpha and PGE2. Cetraxate accelerated the recovery of gastric mucosal PGD2 and 6-keto-PGF1 alpha levels, especially the former. These results suggest that PGs, especially PGD2, are linked with the healing processes of stress ulcers.